Question

when a boy jumps on his bed, his feet push the bed down. what is the reaction force?

a. the bed pushes his feet up.

b. his gravity pulls up on the bed.

c. his gravity pulls up on earth.

d. the bed pushes down on the ground.

Explanation:

To solve this, we use Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. The action here is the boy's feet pushing the bed down (action force). The reaction force should be the bed exerting a force on the boy's feet in the opposite direction.

• Option A: The bed pushing his feet up is the opposite reaction to his feet pushing the bed down, which fits Newton's Third Law.
• Option B: Gravity is a force between the boy and Earth, not directly related to the interaction between the boy's feet and the bed here.
• Option C: This is about the boy's gravity and Earth, not the bed - boy interaction.
• Option D: The bed pushing down on the ground is a different interaction (bed - ground) and not the reaction to the boy's feet pushing the bed.

Answer:

A. The bed pushes his feet up.